Vehicles with a hoist system, such as dump trucks or dump trailers, can generally be used year-round. But such vehicles can be prone to unstable positions and even prone to catastrophic tip-over. Such vehicle tip-over tendencies are believed to be contributing to dramatically climbing insurance rates for hoist style vehicles, including trailer dump bodies and chassis-mounted dump bodies. Moreover, the operation of hoist style vehicles can also encounter problems by overhead utility lines or other obstacles such as bridges, vegetation, etc. which can make it difficult to operate the hoist safely and/or fully.
In contrast to hoist system vehicles, vehicles with a belt conveyor or “live-bottom” dump system do not tend to tip over or to interfere with overhead objects such as utility lines, bridges, and vegetation. However, vehicles with conveyor belts in the prior art generally cannot be used in the winter months and cannot haul some materials due to damage to the conveyor system, for example when materials being hauled damage the chain or belt.
Live-bottom vehicles are vehicles having an endless conveyor system that may be used to unload materials within the vehicle. One type of prior art live-bottom vehicle includes a length of roller chain extending along each side of the trailer with attached cross-members extending therebetween, and a belt fastened to the top of the chain. Another type of prior art live-bottom vehicle includes roller chains, and a belt that surrounds but is not fastened to the chain. In this type of live-bottom vehicle, the roller chain is driven and the weight of the load material on the belt maintains frictional contact between the chain and the belt that is sufficient to cause travel of the belt as the chain is rotated.
Another type of prior art live-bottom vehicle uses a conveyor belt that travels over a solid floor of the vehicle; however, live-bottom vehicles of this type can suffer from several drawbacks. Generally, this type of live-bottom-trailer typically does not provide proper tensioning of the belt. Poor tensioning causes belt slippage and a loss of traction which typically results in poor unloading ability. In some cases, poor tensioning may result in a total loss of traction and drive capability, necessitating manual unloading of the trailer. Further, this type of live-bottom trailer often experiences problems associated with tracking of the belt. Tracking of the belt is important for proper operation of the conveyor and good unloading ability. There exists a continuing need for improved vehicle conveyor systems.